Many gasoline service stations require the installation of multi product fuel dispensers or pumps, each for dispensing a plurality of gasoline products having different octane ratings at each fueling station. Several known systems of this type typically include a separate flow path for each fuel product from its storage tank to the outlet nozzle which introduces it into the consumer's automobile. These systems therefore require the duplication of the components disposed between the tank and the nozzle for each fuel product, including the flow meter. U.S. Pat. No. 5,332,011, which is assigned to the assignee of the present invention, discloses such a dispenser in which three nozzles, fuel hoses and flow meters, each for a different grade of gasoline, are combined in a single dispenser.
There are many disadvantages in these discrete delivery systems. For example, the cost of the system is increased due to the requirement for multiple hoses, nozzles and flow meters. Also, the overall size and space requirements are increased due to the requirement to house the multiple components. In addition, the cost of maintenance and repairs is increased for each discrete delivery system, especially with respect to the flow meters.
In an effort to overcome some of the above problems, multi product fuel dispensers have been developed in which the supply lines from the respective storage tanks are manifolded into a single fuel hose downstream of the flow meters, which hose then leads to a single nozzle. Although this eliminates the multiplicity of nozzles and hoses, the problems associated with the multiplicity of flow meters, such as complexity, space limitations, and repair and maintenance expenses, remain.
Although there have been some designs that have reduced costs by utilizing a single flow meter for a multiple of fuels, they lead to still other problems. For example, in these arrangements a blended fuel is obtained by combining a relatively high octane fuel product with a relatively low octane product, with the desired octane blend ratio being achieved by controlling the flow through a proportional flow control valve associated with each fuel product. However this can lead to significant inaccuracies in the octane of the blended product since the latter is dependent on the actual octane rating of the fuel products in the storage tanks which can vary significantly. Therefore, regardless of the precision of the dispenser blending system in these arrangements, the octane of the blended product delivered through the hose is only as accurate as the purported grade rating of the fuel products in the storage tanks.
Therefore what is needed is a multi product fuel dispensing system in which a blended fuel is derived from a plurality of fuel products with different octane ratings, with the octane content of the blended fuel being independent of any variations in the octane rating of the individual fuel products. What is also needed is a system of the above type which can produce a blended octane fuel that is extremely accurate with respect to its octane rating.